Transmission pattern indication and selection for sidelink grant free transmission

ABSTRACT

With sidelink reservation signals sent together with the sidelink data, there is the possibility of interference with other sidelink signals. In order to address this, systems and methods are provided in which a first UE transmits a reservation signal to indicate at least one time-frequency resource for transmitting sidelink data. Following this, the first UE transmits at least one sidelink data transmission to a second UE using the at least one time-frequency resource indicated by the reservation signal. The reservation signal is transmitted before the at least one sidelink data transmission signal so that a third UE may detect the reservation signal and use the reservation signal to avoid using the at least one time-frequency resource indicated in the reservation signal.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/737,170, filed on Jan. 8, 2020, and entitled “Transmission PatternIndication and Selection for Sidelink Grant Free Transmission,” whichclaims the benefit of U.S. Provisional Patent Application No.62/791,722, filed Jan. 11, 2019, and entitled “Transmission PatternIndication and Selection for Sidelink Grant Free Transmission,”applications of which are incorporated in their entireties herein byreference.

TECHNICAL FIELD

The application relates to systems and methods of selecting andindicating transmission patterns for sidelink grant free transmission.

BACKGROUND

Vehicle to everything (V2X) refers to a category of communicationsscenarios (along with their corresponding technical challenges),including communication between a vehicle and another vehicle (V2V),vehicle to infrastructure (V2I), vehicle to pedestrian (V2P), and manyother scenarios. In V2X, the transmission can be done through a linkbetween network and user equipment (UE), such as uplink (UL) anddownlink (DL) or a sidelink between UE and UE (SL). UE cooperation canbe used to enhance the reliability, throughput, and capacity of V2Xcommunications, as well as next generation wireless communications ingeneral.

LTE V2X: In Long Term Evolution (LTE), a conventional V2X transmissionscheme relies on the concept of a transmit resource pool (RP). Theconventional LTE V2X transmission scheme includes two transmissionmodes: mode 3 and mode 4. In mode 3, a base station (BS) schedulestime-frequency resources (from the UE's RP) for SL transmission usingdownlink control information (DCI), either dynamically orsemi-persistently. In mode 4, a UE randomly selects resources within itstransmit RP. A UE may also reselect resources based on previousmeasurement and sensing results.

The conventional resource pool approach has downsides and limitations.For example, the scheduling in mode 3 results in scheduling-relatedlimitations, such as latency and having the SL transmission rely on DCI.For another example, when the UE autonomously selects resources in mode4, there can be a collision or conflict with the same resource beingselected by another UE.

NR-V2X: In New Radio (NR) Release 16, the following agreement has beenreached for Mode 2:

-   -   For out of coverage operation, Mode-2(c) assumes        (pre)-configuration of single or multiple sidelink transmission        patterns (patterns are defined on each sidelink resource pool);    -   For in-coverage operation, Mode-2(c) assumes that gNB        configuration indicates single or multiple sidelink transmission        patterns (patterns are defined on each sidelink resource pool);    -   If a single pattern is configured to a transmitting UE there is        no sensing procedure executed by the UE;    -   If multiple patterns are configured to a transmitting UE there        is a possibility of a sensing procedure executed by the UE;    -   Pattern is defined in terms of the size of the resource in time        and frequency, Position(s) of the resource in time and        frequency, and the number of resources; and

NR's UL grant-free transmission is called “configured grant ULtransmission” or “UL transmission without dynamic scheduling.” Itincludes two types. For configured grant Type 1, a resource isconfigured by radio resource control (RRC) signaling. For configuredgrant Type 2, a resource is configured by a combination of RRC signalingand DCI signaling. Configured grant type 1 transmission is mainly usedfor uplink transmission, which means the base station that configuredthe resource is also the receiver. Therefore, the receiver (the BS)knows all the configuration of the configured grant UE.

SUMMARY

According to one aspect of the present disclosure, there is provided amethod comprising: transmitting, by a first user equipment (UE) to asecond UE, a first reservation signal to indicate at least onetime-frequency resource for transmitting sidelink data; transmitting, bythe first UE to the second UE, at least one sidelink data transmissionusing the at least one time-frequency resource indicated by the firstreservation signal; wherein the first reservation signal is transmittedbefore the at least one sidelink data transmission signal so that athird UE may detect the first reservation signal and use the firstreservation signal to avoid using the at least one time-frequencyresource indicated in the first reservation signal.

Optionally, wherein the at least one time-frequency resource is at leasttwo time-frequency resources in different time slots, and the at leastone sidelink data transmission is at least two sidelink datatransmissions, each of the time-frequency resources for transmitting arespective sidelink data transmission, and the at least two sidelinkdata transmissions for transmitting a transport block (TB) and at leastone retransmission of the TB to the second UE.

Optionally, the reservation signal is transmitted in a different timeslot than the at least one sidelink data transmission.

Optionally, the reservation signal is an SCI (sidelink controlinformation).

Optionally, wherein the at least one time-frequency resource is apattern, and the reservation signal further indicates a periodicity ofthe pattern.

According to another aspect of the present disclosure, there is provideda method comprising: receiving, by a first user equipment (UE) from asecond UE, a reservation signal to indicate at least one time-frequencyresource for receiving sidelink data; receiving, by the first UE fromthe second UE, at least one sidelink data transmission using the atleast one time-frequency resource indicated by the reservation signal,the reservation signal having been transmitted before the at least onesidelink data transmission signal so that a third UE may detect thefirst reservation signal to avoid using the at least one time-frequencyresource indicated in the first reservation signal.

Optionally, the at least one time-frequency resource is at least twotime-frequency resources in different time slots, and the at least onesidelink data transmission is at least two sidelink data transmissions,each of the time-frequency resources for receiving a respective sidelinkdata transmission, and the at least two sidelink data transmissions forreceiving a transport block (TB) and at least one retransmission of theTB from the second UE.

Optionally, the reservation signal is received in a different time slotthan the at least one sidelink data transmission.

Optionally, the reservation signal is an SCI (sidelink controlinformation).

Optionally, the at least one time-frequency resource is a pattern, andthe reservation signal further indicates a periodicity of the pattern.

According to another aspect of the present disclosure, there is providedmethod comprising: receiving, by a first user equipment (UE) from asecond UE, a first reservation signal to indicate at least onetime-frequency resource for at least one sidelink data transmission fromthe second UE to a third UE, the first reservation signal for the firstUE to avoid using the at least one time-frequency resource; andtransmitting, by the first UE, a second reservation signal indicating atleast one time-frequency resource for at least one sidelink transmissionfrom the first UE to another UE.

Optionally, the method further comprises: prior to transmitting thesecond reservation signal, selecting the at least one time-frequencyresource for the at least one sidelink transmission from the first UE tothe another UE based on the first reservation signal.

Optionally, the method further comprises: prior to receiving the firstreservation signal, selecting at least one time-frequency resource forthe at least one sidelink transmission from the first UE to the anotherUE; after receiving the first reservation signal, determining acollision between the at least one time-frequency resource of the firstreservation signal and the at least one time-frequency resource selectedfor the at least one sidelink transmission from the first UE to theother UE; re-selecting the at least one time-frequency resource for theat least one sidelink transmission from the first UE to the other UE;and wherein the second reservation signal indicates the re-selected atleast one time-frequency resource for the at least one sidelinktransmission from the first UE to the other UE.

According to another aspect of the present disclosure, there is provideda user equipment (UE) comprising: a processor and memory, the UEconfigured to: transmit, by the UE to a second UE, a first reservationsignal to indicate at least one time-frequency resource for transmittingsidelink data; transmit, by the UE to the second UE, at least onesidelink data transmission using the at least one time-frequencyresource indicated by the first reservation signal; wherein the UE isconfigured to transmit the first reservation signal before the at leastone sidelink data transmission signal so that a third UE may detect thefirst reservation signal and use the first reservation signal to avoidusing the at least one time-frequency resource indicated in the firstreservation signal.

Optionally, the at least one time-frequency resource is at least twotime-frequency resources in different time slots, and the at least onesidelink data transmission is at least two sidelink data transmissions,each of the time-frequency resources for transmitting a respectivesidelink data transmission, and the at least two sidelink datatransmissions for transmitting a transport block (TB) and at least oneretransmission of the TB to the second UE.

Optionally, the UE is configured to transmit the reservation signal isin a different time slot than the at least one sidelink datatransmission.

Optionally, the reservation signal is an SCI (sidelink controlinformation).

Optionally, the at least one time-frequency resource is a pattern, andthe reservation signal further indicates a periodicity of the pattern.

According to another aspect of the present disclosure, there is provideda UE comprising: a processor and memory, the UE configured to: receive,by the user equipment (UE) from a second UE, a reservation signal toindicate at least one time-frequency resource for receiving sidelinkdata; receive, by the UE from the second UE, at least one sidelink datatransmission using the at least one time-frequency resource indicated bythe reservation signal, the reservation signal having been transmittedbefore the at least one sidelink data transmission signal so that athird UE may detect the first reservation signal to avoid using the atleast one time-frequency resource indicated in the first reservationsignal.

Optionally, the at least one time-frequency resource is at least twotime-frequency resources in different time slots, and the at least onesidelink data transmission is at least two sidelink data transmissions,each of the time-frequency resources for receiving a respective sidelinkdata transmission, and the at least two sidelink data transmissions forreceiving a transport block (TB) and at least one retransmission of theTB from the second UE.

Optionally, the reservation signal is received in a different time slotthan the at least one sidelink data transmission.

Optionally, the reservation signal is an SCI (sidelink controlinformation).

Optionally, the at least one time-frequency resource is a pattern, andthe reservation signal further indicates a periodicity of the pattern.

According to another aspect of the present disclosure, there is provideda UE comprising: a processor and memory, the UE configured to: receive,by the user equipment (UE) from a second UE, a first reservation signalto indicate at least one time-frequency resource for at least onesidelink data transmission from the second UE to a third UE, the firstreservation signal for the first UE to avoid using the at least onetime-frequency resource; and transmit, by the UE, a second reservationsignal indicating at least one time-frequency resource for at least onesidelink transmission from the first UE to another UE.

Optionally, the UE is further configured to: prior to transmitting thesecond reservation signal, select the at least one time-frequencyresource for the at least one sidelink transmission from the first UE tothe another UE based on the first reservation signal.

Optionally, the UE is further configured to: prior to receiving thefirst reservation signal, select at least one time-frequency resourcefor the at least one sidelink transmission from the first UE to theanother UE; after receiving the first reservation signal, determine acollision between the at least one time-frequency resource of the firstreservation signal and the at least one time-frequency resource selectedfor the at least one sidelink transmission from the first UE to theother UE; re-select the at least one time-frequency resource for the atleast one sidelink transmission from the first UE to the other UE; andwherein the second reservation signal indicates the re-selected at leastone time-frequency resource for the at least one sidelink transmissionfrom the first UE to the other UE.

According to one aspect of the present disclosure, there is provided amethod comprising: transmitting a non-control signal based transmissionresource indication signal (NCSBTRIS) to indicate a transmissionresource; transmitting at least one sidelink data transmission using thetransmission pattern indicated by the NCSBTRIS.

In some embodiments, the NCSBTRIS is one of: a reference signal; asounding reference symbol; a channel state information—reference symbol;a preamble; a synchronization signal; a reservation signal.

In some embodiments, transmitting a NCSBTRIS comprises transmitting ademodulation reference symbol (DMRS).

In some embodiments, the NCSBTRIS is associated with a transmissionresource based on one or a combination of two or more of: DMRS sequence;root or initialization for DMRS sequence; DMRS location; orthogonalcover code used for DMRS.

In some embodiments, the method further comprises randomly selecting aDMRS from a DMRS pool associated with the transmission pattern; whereintransmitting the DMRS comprises transmitting the randomly selected DMRS.

In some embodiments, the method further comprises transmitting theNCSBTRIS multiple times in association with multiple sidelink datatransmissions, or transmitting a NCSBTRIS tuple in association withmultiple sidelink data transmissions, for repetition identification orsoft combining of the multiple sidelink data transmissions.

In some embodiments, the NCSBTRIS transmitted multiple times or theNCSBTRIS tuple indicates redundancy version for the multiple sidelinkdata transmissions.

In some embodiments, transmitting the NCSBTRIS occurs beforetransmitting the at least one sidelink data transmission.

In some embodiments, the NCSBTRIS is transmitted in a first window, andthe at least one sidelink data transmission is transmitted in a secondwindow that is after the first window.

In some embodiments, the method further comprises randomly selecting aresource within the first window to send the NCSBTRIS; or transmittingthe NCSBTRIS using a predefined resource within the first window.

In some embodiments, the method further comprises detecting NCSBTRIStransmitted by other UEs during the first window, and selecting atransmission pattern based on avoiding collision with other UE'stransmission patterns.

In some embodiments the NCSBTRIS is transmitted in a first window, andan initial data transmission is also transmitted in the first window,and remaining repetitions are transmitted in a second window that isafter the first window.

In some embodiments, the method further comprises detecting NCSBTRIStransmitted by other UEs during the first window, and selecting atransmission pattern for the remaining repetitions based on avoidingcollision with other UE's transmission patterns.

In some embodiments, the method further comprises wherein indicating thetransmission resource comprises indicating a transmission pattern.

According to another aspect of the present disclosure, there is provideda method comprising: obtaining a transmission pattern to use for asidelink data transmission, wherein the obtained transmission pattern isa default or configured initial transmission pattern or a transmissionpattern selected from among a pattern pool; performing sensing todetermine transmission pattern(s) used by other UE(s); based on thesensing, selecting between the obtained transmission pattern and adifferent transmission pattern within a pattern pool to use for thesidelink data transmission; transmitting the sidelink data transmissionusing the selected transmission pattern, and also transmitting anindication of the selected transmission pattern.

In some embodiments, performing sensing comprises one or a combinationof: Measurement of RSRP; Measurement of RSSI; Detection of DMRSsequences; Measurement of energy on particular possible transmitresources; Detection of transmission pattern indication signal;Detection of SCI.

In some embodiments, performing sensing comprises sensing during a firsttime window that precedes a time window for data transmission.

In some embodiments performing sensing comprises sensing during a firsttime window that is also used for initial transmissions precedes a timewindow for remaining data transmissions.

In some embodiments, the method further comprises performing short termsensing immediately before sidelink data transmission, and based on thesensing determining whether to perform the transmission or delay thetransmission.

According to another aspect of the present disclosure, there is provideda method comprising: receive a non-control signal based transmissionresource indication signal (NCSBTRIS) to indicate a transmissionresource; receive at least one sidelink data transmission using thetransmission pattern indicated by the NCSBTRIS.

In some embodiments, the NCSBTRIS is one of: a reference signal; asounding reference symbol; a channel state information—reference symbol;a preamble; a synchronization signal; a reservation signal.

In some embodiments, receiving a NCSBTRIS comprises receiving ademodulation reference symbol (DMRS).

In some embodiments, the NCSBTRIS is associated with a transmissionresource based on one or a combination of two or more of: DMRS sequence;root or initialization for DMRS sequence; DMRS location; orthogonalcover code used for DMRS.

In some embodiments, the method further comprises receiving the NCSBTRISmultiple times in association with multiple sidelink data transmissions,or receiving a NCSBTRIS tuple in association with multiple sidelink datatransmissions, for repetition identification or soft combining of themultiple sidelink data transmissions.

In some embodiments, the NCSBTRIS transmitted multiple times or theNCSBTRIS tuple indicates redundancy version for the multiple sidelinkdata transmissions.

In some embodiments, receiving the NCSBTRIS occurs before receiving theat least one sidelink data transmission.

In some embodiments, the NCSBTRIS is received in a first window, and theat least one sidelink data transmission is received in a second windowthat is after the first window.

In some embodiments, the NCSBTRIS is received in a first window, and aninitial data transmission is also received in the first window, andremaining repetitions are received in a second window that is after thefirst window.

In some embodiments, indicating the transmission resource comprisesindicating a transmission pattern.

According to another aspect of the present disclosure, there is provideda user equipment comprising: a processor and memory; at least oneantenna; wherein the user equipment is configured to: perform the methodas described herein.

According to another aspect of the present disclosure, there is provideda user equipment comprising: a processor and memory; at least oneantenna; wherein the user equipment is configured to: perform the methodas described herein as a transmitting user equipment and to perform themethod as described herein as a receiving user equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure will now be described with reference tothe attached drawings in which:

FIG. 1A is a block diagram illustrating an example of a two-dimensionalresource configuration for grant-free SL transmission.

FIGS. 1B-1K are block diagrams illustrating other examples oftwo-dimensional resource configurations for grant-free SL transmission.

FIG. 2 is an example of transmitting an advance indication signal in adedicated indication signal window to indicate transmission resource orpattern for SL transmission;

FIG. 3 is an example of transmitting an advance indication signal toindicate transmission resource or pattern for SL transmission, where theadvance signal is transmitted in an initial transmission window alsoavailable for initial transmissions;

FIGS. 4 and 5 are flowcharts of methods of sidelink transmissionprovided by embodiments of the disclosure;

FIG. 6 is a block diagram illustrating an example of atelecommunications network according to one embodiment;

FIG. 7 is a block diagram illustrating an example of a network servingtwo UEs; and

FIG. 8 is a flowchart of a method of sidelink transmission provided byan embodiment of the disclosure;

FIG. 9 is an of pattern pool replication in the time domain; and

FIG. 10 is example of partially overlapping TFRP pools.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

For illustrative purposes, specific example embodiments will beexplained in greater detail below in conjunction with the figures. Itshould be appreciated, however, that the present disclosure providesmany applicable concepts that can be embodied in a wide variety ofspecific contexts. The specific embodiments discussed are merelyillustrative and do not limit the scope of the present disclosure.

A conventional long-term evolution (LTE) SL transmission scheme relieson the concept of a resource pool (RP) defining a pool of communicationresources that are available for SL communication. The SL is used forboth transmit (Tx) and receive (Rx) functions, and a UE may not be ableto both transmit and receive communications at the same time, i.e., itcan either transmit or receive sidelink communications at one time. Thisis because UEs are typically half duplex devices.

The conventional LTE SL transmission scheme includes two transmissionmodes, known as “mode 3” and “mode 4”.

In mode 3, a BS transmits to a UE control information using a “downlinkcontrol information” (DCI), which schedules time-domain andfrequency-domain communication resources (from an RP) for SLtransmission. This scheduling may be performed dynamically orsemi-persistently using a DCI. However, scheduling of the SLtransmission resources by the BS results in latency. Before the UE cantransmit on the SL, it must wait for the DCI from the BS. Furthermore,the dynamic nature of the resource scheduling increases the signalingoverhead associated with an SL transmission.

In mode 4, the UE autonomously selects resources within the RP, whichavoids the latency issue associated with mode 3. However, the RP in mode4 is not designed to prevent two UEs from selecting the same resourcefor SL communication. Since there is no direct control, by the networkor the BS, of the resources used for SL communication within the RP, twoUEs can cause a message collision by independently selecting the sameresource. When this happens, the collision may cause reliability issuesfor the message, which may not be successfully decoded by the intendedreceivers.

In conventional UL transmissions, whether they be grant-based or“grant-free,” the BS knows the parameters and resources used for the ULtransmission because those parameters and resources are configured bythe BS. This greatly reduces the complexity of the UL transmission, andparticularly it does not require uplink control signaling to beassociated with the UL transmission to indicate the transmissionresources and parameters used for the UL transmission. In a grant-basedUL transmission, for example, the required transmission parameters aretypically communicated to a UE via a Physical Downlink Control Channel(PDCCH). The base station is aware of the identity of the UE sending theUL transmission using the granted UL resources, because the BSspecifically granted those UL resources to that UE in a scheduling grantsent in PDCCH.

In a conventional UL grant-free transmission from a UE to a BS, forexample, different UEs could send UL transmissions using ULcommunication resources configured semi-statically in UE-specific RRCsignaling, without specifically requesting use of the resources in adynamic manner, and without receiving a dynamic scheduling grant of theresources sent in a DCI by the BS. The grant-free transmission typicallyachieves low latency and reduced scheduling overhead as compared to thegrant-based UL transmission. The BS receiving the grant-free ULtransmission knows the communication parameters of the UL transmissionbecause the BS has previously configured the UE performing thegrant-free UL transmission semi-statically. Although, the BS may nothave complete information about which UE, if any, is sending agrant-free UL transmission at a particular moment of time if multipleUEs are configured to be able to access the same resources, the BS isable to detect the grant-free transmissions and determine the UE basedon the configuration parameters (e.g. using DMRS parameters and time andfrequency resources).

While it is also desirable to achieve the advantages of grant-freetransmission for SL communications between UEs, the nature of SLcommunications creates particular challenges for implementing grant-freetransmissions. In contrast to UL grant-free transmissions where thereceiver is a BS with high awareness, both the transmitter and receiverare UEs in SL grant-free transmissions. Therefore, the receiving UE isnot aware of the transmitting UE's configuration parameters, such aswhich UE is transmitting, the ultimate target of the data (e.g., anotherUE), the time-domain and frequency-domain communication resources usedfor the transmission, and other control information.

Grant-free transmissions are sometimes called “grant-less”, “schedulefree”, or “schedule-less” transmissions. Grant-free SL transmission canalso be referred to as SL “transmission without grant”, “transmissionwithout dynamic grant”, “transmission without dynamic scheduling”, or“transmission using configured grant”, for example.

The term collision as used herein refers to a situation in whichmultiple UEs are transmitting signals using the same communicationresource or overlapping communication resources, such that the multipleUEs' transmission signals may interfere with each other, making it moredifficult for the respective receivers to decode the transmittedsignals. For example, a collision occurs when UEs that are transmittingin the same time-frequency resource in the same time slot.

Collision represents an example of a scenario in which an SLtransmission by a UE might not be received by another UE. Half duplexdevices, as noted above, can either transmit or receive sidelinkcommunications at any time. A half duplex UE cannot receive an SLtransmission while it is also transmitting. SL transmission patternscould also or instead be used to mitigate the problem of missing signalsfrom one or more other UEs due to transmitting at the same time.

In some embodiments, an SL transmission pattern represents a sparse setof communication resources. More generally, the SL transmission patterndefines how communication resources are to be used by UEs for SLtransmissions, and can be designed to enable all UEs in a cooperationgroup to communicate with each other even if some transmissions aretransmitted in a grant-free manner (i.e., without dynamic scheduling).This could be especially useful in applications such as V2X and UEcooperation, and/or other applications as well.

In some embodiments, the transmission pattern indicates a number of “on”or usable resources within the time window of the transmission pattern.In a time-frequency based transmission pattern, for example, the UEtransmits using time-frequency communication resources in time slotsthat are designated as “on” time slots by the transmission pattern, andreceives in time slots that are not designated as “on” time slots (orare otherwise designated as “off” time slots) by the transmissionpattern. In this sense, a transmission pattern could be considered aform of “on-off” pattern in some embodiments.

The transmission pattern (or, in some embodiments, the on-off pattern)may define the resources used for a number of transmissions of atransport block (TB). The transmissions may include the initialtransmission and retransmissions of the same TB. The initialtransmission and retransmission of the TB may sometimes also be referredto as repetitions. In some embodiments, each transmission pattern mayrepresent transmissions of one transport block (TB), i.e., a UE shouldstart initial transmission of a TB at the first “on” slot in thetransmission pattern, and continue repetition of the TB on all the “on”slots until the end of the “on” slots defined by the transmissionpattern. In this type of application, a transmission pattern (or on-offpattern) could be considered a repetition pattern. In some embodiments,a UE may also listen to other UE's transmissions in the “off” slotsdefined by the transmission pattern or any slot that is not defined asan “on” slot in the transmission pattern. As described above, referencesignals may be used to accommodate SL data transmission. Someembodiments described herein outline signaling mechanisms that could beused to for grant-free SL communications using transmission patterns.

In some embodiments, a UE is configured to use a transmission patterndefining or otherwise indicating communication resources that areallotted or allocated to the UE over a specific time interval for SLcommunications. Other UEs are similarly configured to use respectivetransmission patterns over this time interval. A UE can transmit andreceive SL transmissions within a time interval using thesecommunication resources according to its transmission pattern. Ahalf-duplex UE might still be transmitting at certain times while otherUEs are transmitting, but transmission patterns could be designed toprovide an opportunity for each UE to receive SL transmissions from allother UEs at least once during the time interval if all UEs areconfigured and transmitting during the time interval using theirrespective transmission patterns.

Time is one dimension that may be used in defining communicationresource usage in a transmission pattern. Other dimensions, such asfrequency, code, and/or signature are also contemplated.

Transmission patterns may belong to a transmission pattern set or poolthat is common to a group of UEs. RRC signaling may be used to configurethe transmission pattern for a UE and/or a transmission pattern pool.Transmission pattern pool may also be signaled by broadcast signaling(e.g. in SIB).

FIG. 1A is a block diagram illustrating an example of a two-dimensionalresource configuration for grant-free SL transmission. This is anexample of a transmission pattern. FIG. 1 illustrates a resource grid100, which includes frequency-domain resources F0, F1, F2 and F3, andtime-domain resources T0, T1, T2, T3 and T4. Each combination offrequency-domain resource and time-domain resource forms a communicationresource for SL transmission. FIG. 1A also illustrates a transmissionpattern for a UE1. Resource grid 100 indicates a time-frequencycommunication resource for two transmissions by UE1, as well as aredundancy version (RV) (RV0 or RV3) in a label on each communicationresource.

In FIG. 1A, UE1 is configured with a transmission pattern, whichexplicitly defines the transmission repetition number as well as thecommunication resources for each repetition. Each repetition may also beassociated with an RV, which can be predefined or preconfigured (e.g.configured using a UE specific RV sequence indicating the associated RVfor each repetition). A single UE index is used to indicate bothtime-domain and frequency-domain resources in FIG. 1A. In general, a UEindex corresponds to a specific UE or a UE group. The communicationresources assigned to UE1 form the transmission pattern for UE1.

The resource grid 100 has a frequency-domain length of 4 and atime-domain length of 5. In the time-domain, T0 to T4 could be slots,mini-slots, symbols, or any other quantization or unit of time. In thefrequency-domain, F0 to F3 could be frequency sub-channels, combinationsof sub-channels, resource blocks, resource block groups (RBGs),bandwidth parts (BWPs), subcarriers, a number of subcarriers, carriersor any other quantization or unit of frequency. Different frequencydomain sub-channels are just an example. Sub-channels can instead beassociated with different layers of non-orthogonal multiple access(NOMA), different pilot resources, and/or other resources. Althoughshown as time-domain resources and frequency-domain resources in FIG.1A, in general the transmission pattern could also or instead includecode-domain resources (such as sparse code multiple access),space-domain resources, and/or different demodulation reference signals(DMRS). Moreover, the transmission patterns are not limited totwo-dimensions, and therefore could include a number of dimensionsgreater or less than two.

In some embodiments, frequency-domain resources, pilots and layer indexmay be associated with time-domain signatures. For example, as analternative to using a UE index, the resource grid 100 could indicateonly the time-domain signature or time-domain transmission pattern, andother dimensions (e.g. the frequency-domain dimension) may be derivedfrom it.

FIG. 1B is another block diagram illustrating an example of atwo-dimensional resource configuration for grant-free SL transmission.FIG. 1B illustrates a resource grid 102. Resource grid 102 includes thesame frequency-domain resources F0, F1, F2 and F3, and time-domainresources T0, T1, T2, T3 and T4 as resource grid 100 in FIG. 1A. FIG. 1Balso illustrates a transmission pattern for UE2.

Resource grid 102 indicates time-frequency communication resources fortwo transmissions by UE2, as well as a redundancy version (RV0 or RV3)in a label on each communication resource. These time-frequencycommunication resources define the transmission pattern for UE2. Thetime-frequency communication resources indicated in resource grid 102for UE2 are different from the time-frequency communication resourcesindicated in resource grid 100 for UE1.

FIGS. 1C, 1D, 1E, 1F, 1G, 1H, 1I and 1J are further block diagramsillustrating other examples of two-dimensional resource configurationsfor grant-free SL transmission. FIGS. 1C, 1D, 1E, 1F, 1G, 1H, 1I and 1Jillustrate resource grids 104, 106, 108, 110, 112, 114, 116 and 118,respectively, each resource grid including the same frequency-domainresources F0, F1, F2 and F3, and time-domain resources T0, T1, T2, T3and T4 as resource grid 100 in FIG. 1A. Resource grids 104, 106, 108,110, 112, 114, 116 and 118 each indicate communication resourcesdefining the transmission patterns for UE3, UE4, UE5, UE6, UE7, UE8, UE9and UE10, respectively, as well as a redundancy version (RV0 or RV3) ina label on each communication resource. Each communication resourceindicated by resource grids 100, 102, 104, 106, 108, 110, 112, 114, 116and 118 are unique.

FIG. 1K is yet another block diagram illustrating a two-dimensionalresource configuration for grant-free SL transmission. FIG. 1Killustrates resource grid 120, which also includes the samefrequency-domain resources F0, F1, F2 and F3, and time-domain resourcesT0, T1, T2, T3 and T4 as resource grid 100 in FIG. 1A. Resource grid 120is a superposition of resource grids 100, 102, 104, 106, 108, 110, 112,114, 116 and 118. Therefore, resource grid 120 may be considered toindicate a transmission pattern pool, which includes the transmissionpatterns for UE1-UE10.

The communication resources illustrated in FIG. 1K are used for SLtransmission by respective UEs, according to their transmissionpatterns. In general, each communication resource represents a potentialtransmission of a transport block (TB). The same TB is used in eachtransmission by a UE over the length of a transmission pattern. In FIG.1K, according to their respective transmission patterns, each UEtransmits a TB twice over the length of the configured transmissionpattern, therefore the repetition number of each transmission pattern is2. As explained below, this allows each UE receive at least onetransmission of the TB by the other UEs.

Embodiments Making Use of Reference Symbol for Pattern Indication

For V2X transmission, it is important to indicate the transmissionpattern, or more generally, the time frequency resource for the SL datatransmissions. The receiver UE may be able to use the information fromthe pattern indication to do decoding of data, combining data fromdifferent transmissions or choosing its own transmission or transmissionpattern to avoid collision with the detected pattern.

As indicated above, one existing way to indicate the transmissionpattern is to indicate it in sidelink control information (SCI)transmitted in a sidelink control channel. SCI may be associated withone or more of the SL data transmissions However, including theinformation in the SCI may incur significant overhead.

In accordance with some embodiments of the disclosure, a non-controlsignal based transmission resource indication signal (NCSBTRIS) istransmitted to indicate transmission resources, for example atransmission pattern, for a sidelink transmission.

In some embodiments, the NCSBTRIS is a reference signal, such as ademodulation reference signal (DMRS). Other specific examples ofreference signals that can be used for the NCSBTRIS include soundingreference signal (SRS), channel state information (CSI)-RS.

In some embodiments, the NCSBTRIS is a preamble.

In some embodiments, the NCSBTRIS is a synchronization signal.

All of these examples of NCSBTRIS have other purposes, such as purposesrelated to channel measurement, channel estimation or synchronizationbut here are also used to implicitly indicate the transmission pattern.

In the following description, the assumption is that the NCSBTRIS is aDMRS, and various options for using the DMRS are provided. It should beunderstood that these same options apply to the other signals that mightbe used for the NCSBTRIS, including other reference signals, preambles,and synchronization signals.

In some embodiments, to indicate the transmission pattern, DMRS has apredefined or a configured mapping/association to the pattern. Theassociation/mapping between DMRS or DMRS parameters and the transmissionpattern (or transmission pattern index) may be predefined. Theassociation/mapping may also be configured to the UE through signaling(e.g. through RRC signaling, system information or preconfigured to theUE). With the mapping, if a UE detects a DMRS, the UE can then derivewhich pattern the transmitter is using. The mapping that is used toassociate DMRS to specific patterns may be based on one or a combinationof DMRS sequence, different roots/initialization for the DMRS sequence,different cyclic shift values, DMRS time and frequency locations (e.g.different symbols), different orthogonal cover code used, differentantenna ports, different code division multiplexing (CDM) groups,different DMRS patterns or some other aspect of the DMRS.

DMRS is mainly used for channel estimation. An example of DMRS can bethe DMRS used in 3GPP NR uplink described in 3GPP TS 38.211 V15.0.0.Another example of DMRS would be the UL DMRS used in LTE. In SLtransmission, similar DMRS structure as LTE or NR uplink may be used.DMRS can be generated using a sequence, such as gold sequence (orm-sequence) or Zadoff Chu sequence. The sequence is usually calculatedusing a root or an initialization value. The sequence may be furtherapplied with a phase shift (some time called a cyclic shift). Forexample, in LTE, a phase shift is applied to the Zadoff Chu sequenceused for uplink DMRS, and the phase shift is usually called cyclic shiftand can be indicated using a cyclic shift value or cyclic shift index.In LTE, the value of cyclic shift is indicated in DCI as one of 8possible choice of cyclic shift value using 3 bits.

The sequence may be further multiplied using an orthogonal cover codes(OCC). The sequence may be further precoded and then mapped to timefrequency resources and modulated to a reference signal and transmittedover the air. Orthogonal cover codes may include orthogonal cover codesapplied to time domain or frequency domain. DMRS sequence may be alsoapplied to time frequency locations (e.g., in different resourceelements) with different allocation patterns. DMRS signal transmittedfrom the same time frequency resource may interfere with each other,therefore it is desirable to design different DMRS that can multiplexedtogether with minimum interference to each other. This can be achievedby using DMRS sequence with low correlation among each other. Anotherway to achieve multiplexing of different DMRS is to use code divisionmultiplexing (CDM), time division multiplexing (TDM) or frequencydivision multiplexing (FDM). Orthogonal cover codes are an example ofCDM. Different allocation patterns (map DMRS sequence to different timefrequency locations) to create different DMRS can be considered TDM orFDM. In some scenarios, the combination of different DMRS properties maybe characterized by a single DMRS parameters, for example in new radio(NR) cellular system, different CDM, TDM, FDM patterns and different OCCused may be indicated using a single parameter as antenna port. Thecombination of DMRS sequence, different allocation patterns (TDM, FDM),different orthogonal cover codes used (different CDM pattern) anddifferent DMRS locations together generates different DMRS.

The DMRS parameter may be known by the UE, then UE can detect DMRSwithout blind detection. In some case, the exact DMRS parameter may notbe known by the UE. In this case, UE can blind decoding DMRS to findwhich DMRS and which DMRS parameters are used. There is usually a finitechoice of DMRS parameters that are known to the UE. An example way to doDMRS detection is to use different choices of potential DMRS sequencesto correlate with the DMRS at the potential location of DMRS and findwhich one gives the highest correlation by finding the output signalwith the highest energy.

For example, In 4G LTE, a Zadoff-Chu (ZC) root sequence may be used togenerate a pool of DMRS sequences generated according to the followingformula

${X_{m,k}^{ZC} = e^{- j\pi q\frac{k({k + 1})}{M_{ZC}}}},$

0≤k<M_(ZC). Where M_{zc} is the length of the root sequence, q is theindex of the reference Zadoff-Chu sequence or the root of the sequence.The reference pilot sequence of given length is the cyclic extension ofthe original Zadoff-Chu sequence. The cyclic shift (phase rotation infrequency domain) of the reference sequence creates multiple orthogonalpilot sequences: X_(k)=X_(k) ^(ZC)e^(−jαk), In LTE α=2mπ/12, m∈{0, 1, .. . , 11}. An orthogonal cover codes may be applied to the two symbolsused for DMRS for each subframe. In this scenario, the root q, cyclicshift value alpha, and the orthogonal cover codes used are allproperties of the DMRS. And UE can do DMRS detection and find out whichroot, which cyclic shift value and which orthogonal cover codes areused. And one or a combination of these properties (roots, cyclic shiftand orthogonal cover codes) may be associate with the transmissionpattern. After receiving UE detecting the DMRS, UE knows thetransmission pattern that the UE who transmit DMRS use by using theassociation between DMRS and the transmission pattern.

In another example, in NR, if transform precoding for PUSCH is notenabled, the reference-signal sequence r(m) shall be generated accordingto

${r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}{\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right).}}}$

where the pseudo-random sequence c(i) is a defined by a length-31 Goldsequence and initialized using some given parameters. There are limitednumber of gold sequences that can be used to generate the DMRS. Afterprecoding, the sequence is mapped to the time frequency resource usingthe following:

The UE shall map the sequence {tilde over (r)}^((p) ^(j) ⁾(m) tophysical resource elements according to

$\begin{matrix}{a_{k,l}^{({p_{j},\mu})} = {\beta_{DMRS}{{w_{f}\left( k^{\prime} \right)} \cdot {w_{t}\left( l^{\prime} \right)} \cdot {{\overset{\sim}{r}}^{(p_{j})}\left( {{2n} + k^{\prime}} \right)}}}} \\{k = \left\{ \begin{matrix}{{4n} + {2k^{\prime}} + \Delta} & {{Configuration}{type}{}1} \\{{6n} + k^{\prime} + \Delta} & {{Configuration}{type}2}\end{matrix} \right.} \\{{k^{\prime} = 0},1} \\{l = {\overset{\_}{l} + l^{\prime}}}\end{matrix}$

where w_(f)(k′), w_(t)(l′), and Δ are given by the specification definedin 3GPP TS 38.211, one of the example table for a configuration type isshown below.

TABLE 6.4.1.1.3-1 Parameters for PUSCH DM-RS configuration type 1. CDMw_(f) (k′) w_(t) (l′) p group Δ k′ = 0 k′ = 1 l′ = 0 l′ = 1 1000 0 0 +1+1 +1 +1 1001 0 0 +1 −1 +1 +1 1002 1 1 +1 +1 +1 +1 1003 1 1 +1 −1 +1 +11004 0 0 +1 +1 +1 −1 1005 0 0 +1 −1 +1 −1 1006 1 1 +1 +1 +1 −1 1007 1 1+1 −1 +1 −1Here Δ value represents different DMRS time-frequency mapping patternsor different TDM/FDM scheme (FDM for this particular example wheredifferent value represents mapping to different subcarriers), which alsocorresponds to different CDM group in this example. w_(f)(k′) andw_(t)(l′) are frequency domain and time domain orthogonal cover codesused. They are all determined using a single antenna port value p thatcan be indicated to the UE. The different gold sequence, orthogonalcover codes (OCC), different mapping pattern together generatesdifferent DMRS. And all the DMRS properties, such as different sequence,time and frequency domain OCC, CDM group, DMRS mapping pattern, antennaports, DMRS locations (such as which DMRS symbols are used) and acombination of them may be used to associate with the transmissionpattern. Again, there may be a limited number of DMRS choices and afterUE detects DMRS, UE can find all the DMRS parameters and obtain thetransmission pattern information using the known DMRS association withthe pattern.

An example of transmission pattern in a given time frequency grid isshown in FIG. 9 , where the same VUE index in the figure represents apattern and VUE index is the pattern index. In the example, there are 20patterns that do not overlap with each other in such a 10 time slots x 4frequency partitions grid.

In one example, DMRS association with the pattern may be achievedthrough a fixed mapping between a DMRS index and a pattern index. TheDMRS index is an index among a pool of DMRS that can indicate acombination of one or multiple DMRS parameters/properties describedearlier. The pattern index can be a known pattern among a pattern pool.For example, if there is 20 DMRS with index p1, p2 . . . p20 there canbe a predefined mapping of p1 to pattern 1, p2 to pattern 2. Etc. Ifthere is 40 DMRS with index p1, p2, . . . , p40, there can be a multipleDMRS to one pattern mapping, e.g., p1 and p2 to pattern 1, p3 and p4 topattern 2, . . . etc.

In some embodiment, DMRS may have a fixed association/mapping with thetransmission pattern or the time frequency location of the transmissionsother than the first transmission of the TB. In some embodiment, DMRSmay have a fixed association/mapping with the transmission pattern orthe time frequency location of the transmissions other than the firsttransmission of the TB given the time frequency location of the firsttransmission of the TB is known.

For example, in some scenario, the first transmission may already beknown by the UE and UE may only need to know the location of the rest oftransmissions of the TB to do combining to decoding the signal. UE canknow the first transmission through decoding of SCI, DMRS, which isassociated with a data transmission. In this case, DMRS may only need tomap to the pattern of the remaining transmissions given the firsttransmission. In the pattern pool defined in FIG. 7 above, once UE findan initial transmission, the location of the second transmission isalready determined, so detecting DMRS may not even be needed to find thelocation of the second transmission.

In another example, the pattern pool is defined as in FIG. 10 , wherethe pattern are partially overlapped with each other. In every timefrequency resource, there are 3 possible patterns. In this case, if a UEfind a first transmission through decoding SCI or DMRS, there may be 3possibilities of transmission pattern or location of second transmissiongiven the location of the first transmission. In this case, 3 DMRS orDMRS groups may be enough to indicate all possible transmissionpatterns. For example, DMRS with index p1 or DMRS in group 1 mayindicate or have a fixed association of patterns in the top figure ofFIG. 8 . DMRS with index p2 or DMRS in group 2 may indicate or have afixed association of patterns in the middle figure of FIG. 8 . DMRS withindex p3 or DMRS in group 3 may indicate or have a fixed association ofpatterns in the bottom figure of FIG. 10 .

After obtain the pattern information through DMRS mapping, UE cancombine the signal from different transmissions through patterninformation to decode the signal. This is most useful in the case wherethe signal is targeting to the UE himself. If the signal is nottargeting the UE, UE may use the pattern information to avoid collisionwith the UE who send the DMRS or pattern indication signal.

In some embodiments, a single pattern can be mapped to multiple DMRS, soa UE may use different DMRS even if it uses the same pattern. Themapping between DMRS and pattern may be predefined or configured by thebase station or the network.

In some embodiments, a UE is preconfigured/-configured/predefined with aDMRS pool and the UE randomly selects a DMRS from the DMRS pool.Alternatively, a UE may be configured/preconfigured with a specificDMRS. A DMRS pool/specific DMRS may be defined among the DMRS mapped tothe same pattern that is to be indicated using the DMRS.

When multiple DMRS are mapped to the same transmission pattern, toindicate a given transmission pattern, a UE may randomly select the DMRSamong the DMRS that can mapped to the pattern.

In some embodiments, a UE also uses multiple transmissions of the sameDMRS or a DMRS tuple (a number of DMRS used for multipletransmission/repetitions) for repetition identification for softcombining. For example, repetition of the same transport block (TB) mayuse the same DMRS or a predefined configured DMRS tuple. DMRS may alsobe used to indicate redundancy version (RV). So once a UE detects theDMRS, the UE also knows how to combine the repetitions.

An example of DMRS tuple associated with retransmission is shown in thetable below, where p11, p21, . . . , p33 are DMRS index. If a UE detectsa P11 DMRS, p21 DMRS, p31 DMRS at different time frequency locations,they knows that they corresponds to the initial transmission, 1^(st)retransmission or repetition of the TB, 2^(nd) retransmission orrepetition of the same TB and can combine all 3 transmissions to decodethe data signal in sidelink transmission.

{P1} {P2} {P3> Index for 3-tuple Initial 1 reT 2 reT 1 P11 p21 p31 2 P12p22 p32 3 P13 p23 p33

In some embodiments, the signal that is used to indicate thetransmission pattern is transmitted contemporaneously with datatransmission. For example, DMRS may be transmitted at the same time orin the same slot as data transmission. In other embodiments, the signalthat is used to indicate the transmission pattern is transmitted inadvance indicate the transmission pattern. An advance indication signalmay be transmitted before the signal transmission occurs, so other UEmay detect the indication signal and use it to avoid a conflict. Anadvance indication signal can be a preamble, a sequence, a RS, areservation signal, a dedicated transmission pattern indication signalto name a few specific examples. In some embodiments, the advancedindication signal may be considered a control signal.

Advantages of using DMRS to indicate transmission pattern includes atleast:

-   -   A reduction in overhead: Depending on the total number of        patterns, transmitting the transmission pattern information in        the SCI may use significant overhead for reliable transmission        of SCI. Using DMRS to indicate the pattern can reduce the        overhead;    -   Reliability: Also DMRS may be more reliable and can be easily        detected even if there are two UEs using the same resource;    -   Other UE can quickly decode DMRS to obtain the pattern        information.

In another embodiment, a dedicated transmission resource indicationsignal is used to indicate a transmission resource, such as atransmission pattern, separate from any SCI associated with a specifictransmission.

Note that a transmission pattern indicated in an SCI is different than aNCSBTRIS or a dedicated transmission resource indication signal. SCI isa control channel that is associated with a specific SL datatransmission, it usually contains information regarding the datatransmission such as scheduling information, transmission parameters orsource/destination ID.

In contrast, a dedicated transmission resource indication signal doesnot directly associate with one SL data transmission; rather, thededicated transmission resource indication signal serves to indicate atransmission pattern for an indefinite number of transmissionssubsequent to the indication.

Decoupling the dedicated transmission resource indication signal from adata transmission has a practical benefit over using SCI to indicate thetransmission resource(s). If the dedicated transmission resourceindication signal is transmitted sufficiently in advance of a datatransmission, a receiver may decode the dedicated transmission resourceindication signal early enough to avoid data transmission collisions. Incontrast, a transmission resource indication over SCI may beinsufficiently in advance of the data transmission (which in most casesare defined to be in the same time slot as the SCI) to guarantee that nocollision will occur on the data transmission.

The dedicated transmission resource indication signal may be transmittedin a channel separate from the SCI's physical sidelink control channel(PSCCH). For example, this separate channel may be a channelspecifically defined for the dedicated transmission resource indicationsignal; alternatively, this dedicated transmission resource indicationsignal may be transmitted in a data channel, such as a physical sidelinkshared channel (PSSCH).

The dedicated transmission resource indication signal may also be knownas a reservation signal. For example, a reservation signal is used forreserving multiple repetitions of a transport block. The dedicatedtransmission resource indication signal could act as a reservationsignal by configuring the repetitions to be the transmission resourcesor transmission pattern defined by the dedicated transmission resourceindication signal.

The dedicated transmission resource indication signal may explicitly orimplicitly indicate the transmission resources or transmission pattern.An explicit indication comprises different bit values being uniquelyassociated with different transmission resources or transmissionpatterns.

Alternatively, an implicit indication may comprise a sequence index orsequence time-frequency location that is uniquely associated withdifferent transmission resources or transmission patterns. For example,receiving an implicit dedicated transmission resource indication signalinvolves a UE receiving a certain information sequence. The index and/ortime-frequency location of the received sequence is associated with apredefined transmission resource or transmission pattern, allowing theUE to implicitly determine the transmission resource or transmissionpattern to be used.

Window for Advanced Transmission of Transmission Pattern IndicationSignal

In some embodiments, a specific window is defined for advancedtransmission of transmission pattern indication signal. Referring now toFIG. 2 , shown is an example of advance transmission of a signal toindicate a transmission pattern. A transmission period T2 is dividedinto a first period 200 between time 0 and time T0, and a second period202 between T0 and T2. The first period 200 is available to transmit thetransmission pattern indication, referred to as the indication signalwindow, and the second period 202 is available for data transmissionusing an indicated transmission pattern, referred to as the datatransmission window. T0 and/or T2 may be predefined and known to the UEor configured/preconfigured to the UE.

A fixed indication period T0 within T2 is defined for transmission ofthe advanced indication signal. In some embodiments, for transmittingthe indication signal, the UE randomly selects a resource from a set ofpossible resources (for example a set of possible time frequencyresources and/or code resources) within the indication signal window tosend the indication signal. Once UE detects the signal, e.g., find outwhich sequence is used to transmit the indication signal, UE can findout the transmission pattern that the UE who send the signal plan touse. Additionally, or alternatively, UE may also beconfigured/preconfigured with a specific time-frequency or code resourcewithin the indication signal window to transmit the indication signal.

In addition, a UE monitors and detects the indication signal(s)transmitted by other UEs within the indication signal window. Based onthe detected indication signal(s), the UE can determine the transmissionpatterns being used by the other UEs. In some embodiments, after the UEdetects other indication signals within the indication signal window,the UE then selects a transmission pattern based on avoiding collisionwith other UE's transmission patterns.

In some embodiments, the transmission pattern pool is defined based on arule where a first transmission is within a first window, and anyretransmissions or further repetitions are in a following window. Forexample, the first window may have a duration T1, and the second windowmay have a duration T2−T1, where T2 is the total duration of the firstand second windows. An example is shown in FIG. 3 which shows an initialtransmission window 320 and a remaining repetition window 322. T1 and/orT2 may be predefined and known to the UE or configured/preconfigured tothe UE.

A reference signal such as DMRS, synchronization signal, preamble or SCIor some other indication is used to indicate the transmission patternused for an initial transmission in the initial transmission window.This indication is transmitted at the same time, same slot or simplyinsufficiently in advance of the data transmission to allow other UE toavoid collision as the initial transmission. Since the indication issent at the same time as the data for the first transmission, thetransmission pattern for the first transmission is not indicated inadvance. As such, another UE may not have time to avoid collision withthe associated data transmission after detecting the correspondingindication signal. However the initial transmission window 320 can beused as a sensing window for sensing indications transmitted by otherUEs so that the UE can attempt to avoid/increase the probability ofavoiding collision for the following repetitions during the remainingrepetition window 322. When the window is defined such that all thetransmission pattern has the first transmission within window T1, UEonly need to monitor the initial transmission within window T1. (throughDMRS detection, SCI detection etc.) to obtain the information ofretransmissions of the TB for other UEs. Therefore, UE can avoid all thecollisions in the second window as no UE is doing initial transmissionin the second window while all the intention for retransmission in thesecond window is detected/known through sensing in the first window withT1.

Transmission Pattern Selection

Some embodiments of the disclosure provide methods of selecting atransmission pattern for a sidelink transmission, when the UE has thefreedom to select between multiple transmission patterns. The methodsinclude steps of configuring transmission patterns,initialization/pattern selection, pattern indication, and sensingtransmission patterns used by other UEs so as to enable the UE to avoidselecting a transmission pattern that is already being used.

Configuration: a UE may have a default transmission pattern or beconfigured with an initial transmission pattern. A UE may beadditionally configured/preconfigured with a transmission pattern pool.The configuration parameters may include one or more of: periodicity,pattern window length, repetition number, time-frequency size of eachtransmission, and/or other configuration parameters. Periodicity is theperiodicity of the resources configured for the UE. Pattern windowlength is length of windows for patterns transmitted within one TB,example of pattern window length is the time between T0 to T4 or 5 slotsfor FIG. 7 . Repetition number is the number of repetitions/transmissionfor each transport block (TB). Time frequency size is the size of timefrequency resources, e.g. number of slots, RBs or subchannels used forone SL data transmission.

Initialization: a UE may use a default or configured initialtransmission pattern as a first selected transmission pattern.Alternatively, if a UE is not configured with an initial pattern, the UEmay be randomly select a transmission pattern among pattern pool.

Pattern indication: When the UE transmits a sidelink data signal usingthe selected transmission pattern, the UE may also indicate the pattern,using any of the previously described methods The indication may betransmitted during the data transmission (e.g. DMRS) or in advance.Alternatively, for this embodiment, the pattern may be indicated in anSCI. Apart from indicating the transmission pattern, SCI may include thegeneral time-frequency resource of the transmission, the indication mayfurther include one or more of periodicity information and reservation(e.g. m TBs to be transmitted in burst) and a priority value. In someother embodiment, SCI may not include time-frequency resource or anyscheduling information such as MCS for the SL data transmission. The mTB refers to that the UE plans to transmit m times or m TBs in mresources that any two neighbor resources are spaced apart by a timedistance defined by periodicity. Each of the m resources for m TB mayinclude more than 1 transmissions of the TB and therefore can have morethan 1 resources. UE may decide to transmit m times and indicate itbecause the packets in the buffer may need to be transmitted m time. Thepriority value indicates how important the transmission with respect toother UEs transmissions is.

Sensing: Various sensing procedures are provided. In some embodiments, aUE may do measurement through reference signal received power (RSRP) ofdata signal, DMRS or SCI, received signal strength indication (RSSI) ofdata signal, DMRS or SCI or through detection of DMRS sequences, orenergy to determine the approximate usage at different possible transmitresources. Based on these measurements, the UE selects a transmissionpattern for sidelink transmission. For example, if for one transmissionpattern, there is too much transmission or too high an amount of energydetected, the UE may select a different transmission pattern.

In some embodiments, a UE detects the transmission pattern indicationsignal (DMRS/preamble/advanced indication signal) or detects an SCI toobtain an indication of the transmission patterns used by other UEs. TheUE may also obtain one or more of periodicity, m reservation andpriority information if included in the transmission pattern indicationsignal and/or SCI. If the UE has selected a transmission pattern thatcollides with one of the patterns determined from the transmissionpattern indication signal or SCI, the UE may re-select a pattern amongthe remaining patterns in the pattern pool.

Note that for sensing, a UE may monitor/detect the indication signal indifferent windows. For example, for the advanced indication signal, a UEmay detect them within a first window of duration T0 as described withreference to FIG. 2 . For the design in FIG. B3 where there is a firsttransmission having duration T1. during which the indication signal andinitial transmissions are transmitted, the UE may detect the indicationsignals of other UEs within T1 and determine a transmission pattern (forone or more remaining transmissions) within T2.

In some embodiments, the UE is configured to avoid all the transmissionpatterns it detected within a predefined sensing period. This may beused with or without a condition that the priority of the detected UE ishigher than the priority assigned to the UE itself. An example is thatthe UE detects an indication (e.g. through SCI or DMRS detection) thatthe transmitting UE plans to transmit m times with periodicity P1, UEmay consider any resources located in t+P1*n, where t is the currenttime, n is the integer between 1 and m a potential resource that used bythe transmitting UE therefore may collide if the UE use the sameresource. In another embodiment, if a UE B detects a pattern used by UEA through any of the method described within a predefined time windowbefore transmission, even if UE A does not reserve another m resources,UE B may assume UE A may keep using the same pattern and therefore tryto avoid use the same pattern in a certain number of subsequenttransmissions. Alternatively, UE A may only avoid such potentialcollision if UE B indicates a higher priority than UE A's transmissionpriority, which may be predefined or configured or simply known by theUE.

In some embodiments, the UE performs short term sensing immediatelybefore the transmission and determines whether it should perform thetransmission or delay the transmission.

For any of the embodiments described above, if changing the transmissionpattern can avoid collision, UE may change the pattern. Otherwise, UEmay use the same selected pattern for the next transmission.

All of the embodiments described herein focus on the use of transmissionpatterns. Various embodiments rely on one or more of NCSBTRIS, advancedindication signal (which may be NCSBTRIS or dedicated pattern indicationsignal, or DCI to indicate the transmission resource for a sidelinktransmission. Transmission patterns were introduced above, and examplesshown in FIGS. 1A to 1K While the embodiments described have focused onthe use of NCSBTRIS or dedicated pattern indication signal or DCI toindicate a transmission pattern, such signals are used to indicatetransmission resources, for example, time frequency resources to be usedfor a sidelink transmission. An indication of a transmission pattern isa specific example of an indication of transmission resources.

In another embodiment, a dedicated transmission resource indicationsignal is used to indicate a transmission resource, such as atransmission pattern, separate from any SCI associated with a specifictransmission.

Note that a transmission pattern indicated in an SCI is different than aNCSBTRIS or a dedicated transmission pattern indication signal. SCI is acontrol channel that is associated with a specific SL data transmission,it usually contains information regarding the data transmission such asscheduling information, transmission parameters or source/destinationID.

In contrast, a dedicated transmission pattern indication signal does notdirectly associate with one SL data transmission, but it indicates atransmission pattern for transmissions subsequent to the indication.

The embodiments described mainly use grant-free or configured grant inNR V2X mode 2 as an example, however, the same approaches can also beused for other transmission modes or methods. For example, theseapproaches may be applicable to UE autonomous transmission based on longterm or short term sensing mode, configured grant transmission in Mode 1etc.

FIG. 4 is a flowchart of another method of sidelink transmissionprovided by an embodiment of the disclosure. The method begins in block400 with transmitting a non-control signal based transmission resourceindication signal (NCSBTRIS) to indicate a transmission resource. Manyexamples of such a signal have been described above. The methodcontinues in block 402 with transmitting at least one sidelink datatransmission using the transmission pattern indicated by the NCSBTRIS.In addition, any of the options/alternatives described herein can beapplied with the method of FIG. 4 .

FIG. 5 is a flowchart of another method of sidelink transmissionprovided by an embodiment of the disclosure. The method begins in block500 with obtaining a transmission pattern to use for a sidelink datatransmission, wherein the obtained transmission pattern is a default orconfigured initial transmission pattern or a transmission patternselected from among a pattern pool. The method continue in block 502with performing sensing to determine transmission pattern(s) used byother UE(s). The method continues in block 504 with, based on thesensing, selecting between the obtained transmission pattern and adifferent transmission pattern within a pattern pool to use for thesidelink data transmission. The method continues in block 506 withtransmitting the sidelink data transmission using the selectedtransmission pattern, and also transmitting an indication of theselected transmission pattern. In addition, any of theoptions/alternatives described herein can be employed with the method ofFIG. 5 .

FIG. 6 is a flow diagram illustrating an example of a method 1300 forsidelink communications. The example method 1300 is illustrative of amethod performed by a user equipment (UE), and involves receiving at1302, by the UE, a message indicating a sidelink (SL) communicationresource configuration. In some embodiments, the configuration includesone or more transmission patterns. For example, the SL communicationresource configuration could define a transmission pattern pool thatincludes multiple transmission patterns.

The communication resource configuration could include a transmissionpattern pool that includes multiple transmission patterns. As shown at1304, a method 1300 could include identifying the transmission patternfor SL data communication, from such a transmission pattern pool.

For example, the UE could belong to a UE group and the transmissionpattern pool could include a transmission pattern pool configured forthe UE group. In these embodiments, the UE could identify a transmissionpattern from among the transmission patterns of the transmission patternpool for the UE group. Identifying the transmission pattern couldinclude identifying the transmission pattern based on a UE index of theUE, and a method could then involve receiving additional signalingassigning the UE index to the UE for example. Such additional signalingcould include downlink control information (DCI) signaling.

Identifying the transmission pattern at 1304 could involve the UEselecting the transmission pattern. The transmission pattern selectionby the UE could be random by UE. Other selection embodiments are alsodisclosed herein, that for example, rely on sensing transmissions ofother UEs.

The example method 1300 also involves transmitting at 1306, by the UE,NCSBTRIS. The NCSBTRIS may indicate the repetition pattern defined bythe SL communication resource configuration. As noted above, in someembodiments the SL communication resource configuration includes atransmission pattern that defines a pattern for transmitting the SL datacommunication. The transmission pattern could define an initialtransmission of a data block and a repetition of the data block. Thetransmission pattern could further define time resources used for theinitial transmission of the data block and the repetition of the datablock. The SL communication resource configuration could further includea starting time of the transmission pattern, and the transmissionpattern further defines a time gap from the initial transmission of thedata block to the repetition of the data block.

The example method 1300 also involves transmitting at 1310, by the UE,an SL data communication according to the indicated transmit pattern.This SL data communication could be transmitted to one UE or to multipleUEs. In some embodiments, the SL data communication includes aretransmission of a data communication.

The example illustrated in FIG. 6 is represents one possible embodiment.However, other embodiments are also possible which could includeadditional features, fewer features, and/or different features thanthose illustrated in FIG. 6 .

FIG. 7 is a block diagram illustrating an example of atelecommunications network 1400 according to one embodiment, forimplementing any one or combination of two or more of the abovedescribed methods. The telecommunications network 1400 includes a corenetwork 1402 and an access network 1406. The access network 1406 servesa plurality of UEs 1404 a, 1404 b, 1404 c, 1404 d, 1404 e, 1404 f, 1404g, 1404 h, and 1404 i. The access network 1406 could be an EvolvedUniversal Terrestrial Access (E-UTRA) network. As another example, theaccess network 1406 could be a cloud access network (C-RAN). The accessnetwork 1406 includes a plurality of BSs 1408 a, 1408 b, and 1408 c. TheBSs 1408 a-c each provide a respective wireless coverage area 1410 a,1410 b, and 1410 c. Each of the BSs 1408 a-c could be implemented usinga radio transceiver, one or more antennas, and associated processingcircuitry, such as antenna radio frequency (RF) circuitry,analog-to-digital/digital-to-analog converters, etc.

Although not illustrated, the BSs 1408 a-c are each connected to thecore network 1402, either directly or through one or more centralprocessing hubs, such as servers. The BSs 1408 a-c could serve as agateway between the wireline and wireless portion of the access network1406.

Each one of BSs 1408 a-c may instead be referred to as a basetransceiver station, a radio BS, a network node, a transmit node, atransmit point, a Node B, an eNode B, or a remote radio head (RRH),depending upon the implementation.

In operation, the plurality of UEs 1404 a-i access thetelecommunications network 1400 using the access network 1406 bywirelessly communicating with one or more of the BSs 1408 a-c.

UEs 1404 a-d are in close proximity to each other. Although the UEs 1404a-d can each wirelessly communicate with the BS 1408 a, they can alsodirectly communicate with each other, as represented at 1416. Thecommunications represented at 1416 are direct communications between UEsthat do not go through an access network component, such as a BS. Asshown in FIG. 14 , UE to UE communications 1416 are directly between theUEs 1404 a-d and are not routed through the BS 1408 a, or any other partof the access network 1406. Communications 1416 may also be referred toas lateral communications. In embodiments disclosed herein, UE to UEcommunications use an SL channel and an SL air interface. On the otherhand, a communication between an access network component, such as BS1408 a, and a UE, as in communication 1414, is called an accesscommunication. An access communication occurs over an access channel,which can be a UL or DL channel, and an access communication uses aradio access communication interface, such as a cellular radio accessair interface. Access and SL air interfaces may use differenttransmission formats, such as different waveforms, different multipleaccess schemes, and/or different radio access technologies. Someexamples of radio access technologies that could be used by an accessair interface and/or an SL air interface are: Long Term Evolution (LTE),LTE License Assisted Access (LTE-LAA), and WiFi.

By using the SL communications 1416, the UEs 1404 a-d may be able toassist with wireless communications between the UEs 1404 a-d and the BS1408 a. As one example, if UE 1404 c fails to correctly decode a packetreceived from the BS 1408 a, but if UE 1404 d is able to receive andcorrectly decode the packet from the BS 1408 a, then UE 1404 d coulddirectly transmit the decoded packet to UE 1404 c using SLcommunications 1416. As another example, if UE 1404 c moves out ofwireless coverage area 1410 c, such that UE 1404 c can no longerwirelessly communicate with the BS 1408 a, then UE 1404 b could forwardmessages between the UE 1404 c and the BS 1408 a. As another example, UE1404 a and UE 1404 c could both receive a signal transmitted from the BS1408 a that carries a packet meant for UE 1404 c. UE 1404 a may thentransmit to UE 1404 c, via SL communications 1416, the signal asreceived by UE 1404 a. UE 1404 c may then use the information receivedfrom UE 1404 a to help decode the packet from the BS 1408 a. In theseexamples, capacity and/or coverage may be enhanced through theassistance of UEs 1404 a, 1404 b, and/or 1404 d. V2X communications asreferenced herein are an example of SL communications.

The UEs 1404 a-d form a UE group 1420. The access network 1406 couldassign a group identifier (ID) to the UE group 1420. The UE group ID mayallow the access network 1406 to address the UE group 1420 as a wholeand distinguish the UE group 1420 from other UE groups. The UE group IDmay also be used to broadcast information within the UE group, i.e.address all other UEs within the UE group 1420. The UE group 1420 mayform a logical or virtual device mesh in which the members of the UEgroup 1420 communicate amongst themselves using UE communications overan SL air interface, but the UE group 1420 as a whole acts as a singledistributed virtual transceiver with respect to the access network 1406.The UE group ID may be a group radio network temporary identifier(G-RNTI), for example.

When a particular UE in the UE group 1420 is being assisted or is to beassisted with wireless communication between that UE and the BS 1408 a,then that particular UE is referred to as the target UE. In the examplesabove, UE 1404 c is being assisted and so is the TUE 1404 c. The otherUEs 1404 a, 1404 b, and 1404 d in the group 1420 form a cooperationcandidate set, which is a set of UEs that may cooperate to help the TUE1404 c. The subset of UEs in the cooperation candidate set that actuallyassist the target UE 1404 c form a cooperation active set. Thecooperation active set may be dynamically selected to assist the targetUE 1404 c. The UEs in the cooperation active set are referred to ascooperating UEs (CUEs). In UE group 1420, UEs 1404 a, 1404 b, and 1404 dform the cooperation candidate set. If UEs 1404 a and 1404 b actuallyassist target UE 1404 c, then UEs 1404 a and 1404 b form the cooperationactive set and are the CUEs. As UEs 1404 a-d move around, some may leavethe UE group 1420 and/or other UEs may join the UE group 1420.Therefore, the cooperation candidate set may change over time, e.g., thecooperation candidate set may change semi-statically. The UE group 1420may also be terminated by the network 1406, e.g., if the networkdetermines that there is no longer a need or opportunity for the UEgroup 1420 to provide assistance in wireless communication between theBS 908 a and members of the UE group 1420.

There may be more than one UE group. For example, UEs 1404 e and 1404 fin FIG. 7 form another UE group 1422.

FIG. 8 is a block diagram illustrating an example of a network 1552serving two UEs 1554 a and 1554 b, according to one embodiment. Thenetwork 1552 may be the access network 1406 from FIG. 7 , and the twoUEs 1554 a and 1554 b may be two of the four UEs 1404 a-d in FIG. 7 , orthe UEs 1554 a and 1554 b may be UEs 1404 e and 1404 f in FIG. 7 .However, more generally this need not be the case, which is whydifferent reference numerals are used in FIG. 8 .

The network 1552 includes a BS 1556 and a managing module 1558. Themanaging module 1558 instructs the BS 856 to perform actions. Themanaging module 858 is illustrated as physically separate from the BS1556 and coupled to the BS 1556 via a communication link 1560. Forexample, the managing module 1558 may be part of a server in the network1552. Alternatively, the managing module 1558 may be part of the BS1556.

The managing module 1558 includes a processor 1562, a memory 1564, and acommunication module 1566. The communication module 1566 is implementedby the processor 1562 when the processor 1562 accesses and executes aseries of instructions stored in the memory 1564, the instructionsdefining the actions of the communication module 1566. When theinstructions are executed, the communication module 1566 causes the BS1556 to perform the actions described herein so that the network 1552can establish, coordinate, instruct, and/or control a UE group.Alternatively, the communication module 1566 may be implemented usingdedicated circuitry, such as an application specific integrated circuit(ASIC) or a programmed field programmable gate array (FPGA).

The UE 1554 a includes a communication subsystem 1570 a, two antennas1572 a and 1574 a, a processor 1576 a, and a memory 1578 a. The UE 1554a also includes a communication module 1580 a. The communication module1580 a is implemented by the processor 1576 a when the processor 1576 aaccesses and executes a series of instructions stored in the memory 1578a, the instructions defining the actions of the communication module1580 a. When the instructions are executed, the communication module1580 a causes the UE 1554 a to perform the actions described herein inrelation to establishing and participating in a UE group. Alternatively,the module 1580 a may be implemented by dedicated circuitry, such as anASIC or an FPGA.

The communication subsystem 1570 a includes processing andtransmit/receive circuitry for sending messages from and receivingmessages at the UE 1554 a. Although one communication subsystem 1570 ais illustrated, the communication subsystem 1570 a may be multiplecommunication subsystems. Antenna 1572 a transmits wirelesscommunication signals to, and receives wireless communications signalsfrom, the BS 1556. Antenna 1574 a transmits SL communication signals to,and receives SL communication signals from, other UEs, including UE 1554b. In some implementations there may not be two separate antennas 1572 aand 1574 a. A single antenna may be used. Alternatively, there may beseveral antennas, but not separated into antennas dedicated only to SLcommunication and antennas dedicated only to communicating with the BS1556.

SL communications could be over Wi-Fi, in which case the antenna 1574 amay be a Wi-Fi antenna. Alternatively, the SL communications could beover Bluetooth™, in which case the antenna 1574 a may be a Bluetooth™antenna. SL communications could also or instead be over licensed orunlicensed spectrum.

The UE 1554 b includes the same components described above with respectto the UE 1554 a. That is, UE 1554 b includes communication subsystem1570 b, antennas 1572 b and 1574 b, processor 1576 b, memory 1578 b, andcommunication module 1580 b.

The UE 1554 a is designated as a target UE (TUE) and will therefore becalled TUE 1554 a. The UE 1554 b is a cooperating UE and will thereforebe called CUE 254 b. The CUE 1554 b may be able to assist with wirelesscommunications between the BS 1556 and TUE 1554 a if a UE group were tobe established that included TUE 1554 a and CUE 1554 b. Othercommunication scenarios are also contemplated, in a V2X application, forexample.

UE 1554 a may be specifically chosen as the target UE by the network1552. Alternatively, the UE 1554 a may itself determine that it wants tobe a target UE and inform the network 1552 by sending a message to theBS 1556. Example reasons why UE 1554 a may choose or be selected by thenetwork 1552 to be a target UE include: low wireless channel qualitybetween the UE 1554 a and the BS 1556, many packets to be communicatedbetween the BS 1556 and the UE 1554 a, and/or the presence of acooperating UE that is a good candidate for helping with communicationsbetween the BS 1556 and the UE 1554 a.

UE 1554 a need not always stay a target UE. For example, UE 1554 a maylose its status as a target UE once there is no longer a need or desirefor assistance with wireless communications between UE 1554 a and the BS1556. UE 1554 a may assist another target UE that is a cooperating UE ata later time. In general, a particular UE may sometimes be a target UEand other times may be a cooperating UE assisting another target UE.Also, sometimes a particular UE may be both a target UE receivingassistance from one or more cooperating UEs and also a cooperating UEitself assisting another target UE. In the examples below, the UE 1554 aacts only as a target UE, i.e., TUE 1554 a, and the UE 1554 b is acooperating UE to the TUE 1554 a, i.e., CUE 1554 b.

FIGS. 7 and 8 illustrate systems in which embodiments could beimplemented. In some embodiments, a UE includes a processor, such as1576 a, 1576 b in FIG. 8 , and a non-transitory computer readablestorage medium, such as 1578 a, 1578 b in FIG. 8 , storing programmingfor execution by the processor. A non-transitory computer readablestorage medium could also or instead be provided separately, as acomputer program product.

In such embodiments, programming could include instructions to: receive,by the UE, a message indicating a sidelink (SL) communication resourceconfiguration to be used by the UE for SL control information and SLdata communications between the UE and another UE; transmit, by the UE,SL control information according to the SL communication resourceconfiguration; and transmit, by the UE, an SL data communicationaccording to the SL communication resource configuration, wherein the SLcontrol information and the SL data communication are transmitted by theUE without receiving, in a downlink control information (DCI), a grantof communication resources.

The instructions to transmit the SL control information could includeinstructions to transmit, by the UE, a scheduling assignment (SA) to theother UE using a communication resource defined in the SL communicationresource configuration, the SA indicating communication resources usedfor transmitting the SL data communication.

The SL communication resource configuration could include a transmissionpattern that defines a pattern for transmitting the SL datacommunication.

The transmission pattern could define an initial transmission of a datablock and a repetition of the data block, and could also define timeresources used for the initial transmission of the data block and therepetition of the data block.

An SL communication resource configuration could include a starting timeof the transmission pattern, and the transmission pattern could furtherdefine a time gap from the initial transmission of the data block to therepetition of the data block.

Instructions to transmit the SL control information could includeinstructions to transmit one instance of the SL control information forboth the initial transmission of the data block and the repetition ofthe data block.

In some embodiments, the instructions to transmit the SL controlinformation include instructions to transmit a separate instance of theSL control information for each of the initial transmission of the datablock and the repetition of the data block.

The programming could also include instructions to listen for SLtransmissions by other UEs during segments of the transmission patternother than the SL transmissions.

One or more other UEs may use a different transmission pattern.

The SL communication resource configuration could define a transmissionpattern pool that includes multiple transmission patterns, as disclosedherein. The programming could then include instructions to identify thetransmission pattern among the transmission patterns of the transmissionpattern pool.

For example, the UE could belong to a UE group and the transmissionpattern pool could include a transmission pattern pool configured forthe UE group. The instructions to identify the transmission patterncould then include instructions to identify the transmission patternbased on a UE index of the UE. The programming could also includeinstructions to receive additional signaling assigning the UE index tothe UE. The additional signaling could be downlink control information(DCI) signaling, for example.

The instructions to identify the transmission pattern could includeinstructions to select the transmission pattern. The selection of thetransmission pattern is random in some embodiments, but other selectionoptions are possible.

The SL communication resource configuration could define a transmissionpattern for transmitting the SL control information. The transmissionpattern for transmitting the SL control information could be the same ordifferent from the transmission pattern for transmitting the SL datacommunication.

The SL communication resource configuration could define communicationresources used for transmitting the SL control information or the SLdata communication, and the communication resources could include atleast one of time-domain resources, frequency-domain resources andcode-domain resources.

The received message indicating the SL communication resourceconfiguration could be a radio resource control (RRC) message asdisclosed by way of example herein, or another type of message such as aMedium Access Control layer Control Element (MAC CE) message.

Embodiments disclosed herein could be useful in mitigating effects ofthe SL half duplex constraint. Embodiments could also improve thelatency and reliability of SL transmissions using a UE specifictransmission pattern, and a distributed transmission mode that can bedesigned to enable all UEs in a cooperation group to communicate witheach other even if some transmissions are affected by collisions or thehalf duplex constraint, for example.

The grant-free transmission modes described herein may be used in NRother than in SL and V2X communication. For example, the grant-freetransmission modes may be applicable in unlicensed transmission.

Although the present invention has been described with reference tospecific features and embodiments thereof, various modifications andcombinations can be made thereto without departing from the invention.The description and drawings are, accordingly, to be regarded simply asan illustration of some embodiments of the invention as defined by theappended claims, and are contemplated to cover any and allmodifications, variations, combinations or equivalents that fall withinthe scope of the present invention. Therefore, although the presentinvention and its advantages have been described in detail, variouschanges, substitutions and alterations can be made herein withoutdeparting from the invention as defined by the appended claims.Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present invention, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present invention. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or steps.

Moreover, any module, component, or device exemplified herein thatexecutes instructions may include or otherwise have access to anon-transitory computer/processor readable storage medium or media forstorage of information, such as computer/processor readableinstructions, data structures, program modules, and/or other data. Anon-exhaustive list of examples of non-transitory computer/processorreadable storage media includes magnetic cassettes, magnetic tape,magnetic disk storage or other magnetic storage devices, optical diskssuch as compact disc read-only memory (CD-ROM), digital video discs ordigital versatile disc (DVDs), Blu-ray Disc™, or other optical storage,volatile and non-volatile, removable and nonremovable media implementedin any method or technology, random-access memory (RAM), read-onlymemory (ROM), electrically erasable programmable read-only memory(EEPROM), flash memory or other memory technology. Any suchnon-transitory computer/processor storage media may be part of a deviceor accessible or connectable thereto. Any application or module hereindescribed may be implemented using computer/processorreadable/executable instructions that may be stored or otherwise held bysuch non-transitory computer/processor readable storage media.

It should also be appreciated that features disclosed herein could beapplied to components other than those specifically referenced by way ofexample, such as V2X infrastructure components including RSUs (i.e., notjust ends and UEs). A roadside unit (RSU) is a stationary transportationinfrastructure entity (e.g., an entity which can transmit speednotifications) supporting V2X applications that can exchange messageswith other entities supporting V2X applications. An RSU is a logicalentity which in addition to supporting V2X applications can also providethe functionalities of a network entity (e.g., eNB, gNB, base station),in which case it may be referred to as an e/gNB-type RSU, or a UE, inwhich case it may be referred to as a UE-type RSU. Network featurestherefore may apply to e/gNB-type RSUs and UE features may apply toUE-type RSUs.

In some embodiments, in order to support the very low latency (e.g. 3 msend-to-end delay) and high reliability requirements (e.g. 99.999%) ofsome NR V2X applications, fast repetition and immediate access to(pre-)configured resources should be supported. LTE Rel. 14/15 V2Xsupports up to two transmissions of the same TB in LTE SL mode 4, andthe retransmission resource may be independently selected from that ofthe original transmission. NR's higher reliability target requires ahigher maximum number of retransmissions, and can be further enhanced byavoiding potential collisions between the SL retransmissions ofdifferent UEs. This can be achieved in a grant-free transmission mode,by (pre)-configuring a pool of two-dimensional time/frequency repetitionpatterns (TFRPs). The TFRPs indicate the time and frequency location ofeach repetition of a TB. The (pre-)configuration takes into account theUE needs and the radio conditions. The TFRP selection is performed atleast once within the periodicity of the (pre-)configured grantresources.

Sensing and Resource Selection

In some embodiments, for mode 2-c UEs (pre-)configured with aUE-specific TFRP, no sensing or resource selection is needed, and formode 2-c UEs (pre-)configured with TFRP pools, TFRP selection is needed.For the TFRP selection, the UE could either pseudo-randomly select apattern or may use some knowledge it obtains either from monitoring thePSCCH or from detecting DMRS. For the former, an indication message onthe selected TFRP can be transmitted to other UEs to improve thereliability of GF transmissions. While transmitting the explicitindication message results in more reliable detection of selected TFRPs,in case of detecting DMRS there could be a mapping between a detectedDMRS and an associated TFRP, so that no TFRP indication message needs tobe sent as part of the SCI, thus saving on signaling overhead. Sensingin the form of SCI decoding and/or DMRS detection can lead to areduction of TFRP collisions. By keeping track of the currently usedpatterns, the UE can select one pattern that does not collide with thein-use patterns.

Numerous modifications and variations of the present disclosure arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the disclosuremay be practiced otherwise than as specifically described herein.

What is claimed is:
 1. A method comprising: transmitting, by a firstuser equipment (UE) to a second UE, a first reservation signal toindicate at least one time-frequency resource for transmitting sidelinkdata; and transmitting, by the first UE to the second UE, at least onesidelink data transmission using the at least one time-frequencyresource indicated by the first reservation signal, wherein the firstreservation signal is transmitted before the at least one sidelink datatransmission signal so that a third UE may detect the first reservationsignal and use the first reservation signal to avoid using the at leastone time-frequency resource indicated in the first reservation signal.